It is known that fuel-cell stacks make it possible to produce electrical power directly, via an electrochemical redox reaction, from a fuel gas and an oxidant gas, without conversion into mechanical energy. This technology seems promising especially for automotive applications. A fuel-cell stack generally includes the association in series of unitary elements that each essentially consist of an anode and a cathode separated by a polymer membrane allowing ions to pass from the anode to the cathode.
Thus, the anode supplied with fuel, for example hydrogen, is the site of an oxidation half-reaction. At the same time, the cathode supplied with oxidant, for example pure oxygen or oxygen contained in air, is the site of a reduction half-reaction. In order for these two half-reactions to be possible, it is necessary to fill the anode and cathode with catalyst, namely a compound capable of increasing the reaction rate without itself being consumed. Among the various catalysts employed, it has been observed that the best performance is obtained using platinum, alone or in alloy form.
In order to prevent any degradation of the fuel-cell stack, and especially of the catalysts, during the many stops/starts undergone in the lifetime of a stack, it is necessary to provide specific stopping procedures, such as that described in patent application EP 2 494 642.
However, the performance of fuel-cell stacks has been observed to decrease after a few stop/start cycles. Therefore, the objective of the present invention is to provide a method allowing the performance of a fuel-cell stack to be maintained without disrupting its operation and without creating supplementary degradation.